Systems for treating liquids, especially for analysis, are applied, for example, in process measurements technology or in industrial measurements technology. For example, analytical systems can be applied for monitoring and optimizing the cleaning effectiveness of a clarification plant, for monitoring drinking water or for quality monitoring of food. Measured and monitored are, for example, the content of special substances in a liquid sample, for example, the content of ions, such as ammonium, phosphate or nitrate, or biological or biochemical compounds, such as hormones, or microorganisms, e.g. bacteria.
Frequently in analytical systems, the sample to be analyzed is mixed with one or more reagents, so that a chemical change occurs in the liquid sample, for example, due to a chemical reaction of the reagent with the substance to be monitored. Preferably, the reagents are so selected that the chemical change is detectable by means of physical methods, for example, by optical measurements. A simple example of such a chemical change can be a color change, which is detectable photometrically, thus with optical means. In the field of bioanalysis, frequently analytical methods are applied according to an assay principle. These rest on a specific binding ability of a binding partner with a biomolecule to be detected. Frequently, the binding partners are so selected that the molecule to be determined, also referred to as the analyte, and the binding partner form an antibody/antigen-system. With the help of physically detectable markers on the analyte, on the binding partner or on a competitor added to the system, which likewise can bind to the binding partner of the analyte, the amount of the specifically bound analyte molecules can be ascertained, and therefrom, the concentration of the analyte in the sample can be deduced. The markers can be in the form of, for example, luminescing molecules, luminescing nano particles or magnetic nano particles. Frequently, the binding partner, to which the analyte specifically binds, is immobilized on a surface; it can, however, also be present in solution.
In order to automate such analytical methods, for example, for industrial applications, it is necessary to provide an analytical system, which performs the desired analytical method automatically. The most important requirements for such an analytical system are, besides a sufficient accuracy of measurement, robustness, simple serviceability and the assurance of a sufficient working, and environmental, safety. Since the reagents used for the analysis are, in part, not directly returnable to the water system, their safe disposal likewise plays an essential role.
In the state of the art, there exist already a large selection of semiautomatic and automatic, analytical systems. Although many of these function without problem, they are frequently relatively complicated in construction, and, consequently, susceptible to defects and, as a rule, only serviceable by trained operating personnel. Thus, for example, DE 102 22 822 A1 discloses an online analyzer for analyzing a sample. The online analyzer is embodied in the form of a device that comes in a cabinet, in which are arranged a control unit, reagent supply containers, pumps for conveying reagents into a mixing cuvette for mixing the reagents with the liquid, a waste container, as well as an optical unit for optical measurements on the liquid sample treated in the mixing cuvette with reagents. The reagents are led via hose connections from the reagent containers and transported into the mixing cuvette. Correspondingly, used liquid is transferred from the mixing cuvette, again, via a hose connection into the waste container. If the waste container or one of the reagent supply containers must be replaced, attention must be paid that the hose connections are then reconnected correctly. The hoses and the conveyor pumps are susceptible to material fatigue and must likewise be subjected to maintenance or replaced from time to time.
Especially in the field of biosensors and medical technology, analytical systems have been developed, in the case of which the treating of the examined sample with reagents is performed by means of technologies, which are known from the technical field referred to generically as “lab on a chip”. Frequently, the sample need only be applied to a prepared chip, which, besides liquid lines for the sample and for reagents, also includes reagent reservoirs as well as functional elements, for example, mixers or valves. The chip can, after application of the sample, be inserted into an analytical device, which performs and controls the treating of the liquid sample with the reagents and performs the corresponding physical measurements on the treated liquid sample. Such a device is described, for example, in US 2009/0126505 A1 or EP 1 967 266 A1. The chips disclosed there are embodied as single-use products, so that a new chip must be used for each analysis.
US 2009/0053814 A1 describes an analytical system with automatically fillable, internal reagent storage and a fluidics system for automatic treating of a liquid sample with the reagents as well as an optical measuring apparatus for detecting chemical changes in the treated sample. Also, this system with syringe pumps, fluidics connections between the pumps and the reagent containers, and valves for switching between an external reagent reservoir and an internal reagent storage is relatively complicated in construction and, thus, maintenance intensive and serviceable only by trained operating personnel.